1. Field of the Invention
The present invention relates to a tape cassette, and more specifically to a tape cassette that has a pair of tape reels capable of winding a tape, typically a magnetic tape for example, there-between into a good shape without causing winding irregularities and deformations such as wrinkles of the wound tape on the tape reels.
2. Description of the Related Art
When considering a magnetic tape for recording and reproducing video and/or audio signals among various tapes used in various technical fields, there are various systems for recording and reproducing audio and video signals, such as the xcex2-VTR system, the VHS-VTR system or the Digital VTR system. A fundamental structure of a tape cassette to be used for each of above mentioned VTR (Video Tape Recorder) systems is basically the same, in which a tape cassette shell houses a take-up reel and a supply reel for winding the magnetic tape. As a matter of course, besides the magnetic tape as described above, there are various kinds of tapes to be wound on tape reels, such as ink ribbon tapes for printers, carrier tapes for electronic parts or the like.
A fundamental structure of each of tape reels within a tape cassette is explained with reference to FIG. 14 and FIG. 15, wherein FIG. 14 shows a perspective view of a tape reel 10 used for a conventional tape cassette and FIG. 15 shows a sectional view of the conventional tape reel 10. An upper flange 2 and a lower flange 13 are provided at a top end and a bottom end of a hub 4 which is positioned at a center of the tape reel 10 to wind a magnetic tape in order to prevent winding irregularities or winding collapse of the magnetic tape as well as to prevent damages of end face edges of the wound magnetic tape. One of the flanges 2 and 13 (namely the lower flange 13 in case of FIGS. 14 and 15) is molded integrally with the hub 4 and the other flange on the other side (namely the upper flange 2 in case of FIGS. 14 and 15) is molded separately as another body, and this upper flange 2 is welded integrally with the upper end face of an inner cylinder 4a of the hub 4. Inside the welded portion, a spring unit 6 having a metallic spherical body is held between the inner cylinder 4a and the upper flange 2. As shown in FIG. 16, this spring unit 6 contacts with a tape reel presser 23 that is provided on an upper shell 22 of the tape cassette and depresses the tape reel 10 downward by a coil spring 24 provided between the upper shell 22 and the tape reel presser 23. Incidentally, regarding flanges of a tape reel, a one-flange type tape reel comprises a hub and a lower flange, besides a two-flange type tape reel comprises a hub, a lower flange and a upper flange as described above.
In manufacturing the magnetic tape cassette, the magnetic tape is wound on a tape winding surface 4q of the hub 4 by a tape winding device called a tape winder. At this time, there easily occur winding irregularities (irregularities on the side surfaces of the wound magnetic tape) and air is considered as the cause of the winding irregularities, wherein the air is caught into between the hub 4 and the magnetic tape being wound thereon, and between the magnetic tape already wound and the magnetic tape being wound up thereon. Besides, there is the case where the magnetic tape is deformed (for instance, creases in the width direction of the magnetic tape that is slightly piled up). These problems tend to easily occur on the inner side of the wound tape.
FIG. 17 shows a plan view of the lower flange 13 of the tape reel 10 used in the conventional tape cassette (hereinafter abbreviated as the tape reel 10), and illustrates the inner surface thereof. As shown in FIG. 17, on the inner surface of the lower flange 13, 12 of concave portions 18 are formed as to extend in a radial direction at even angle intervals of 30 degrees. These concave portions 18 are provided so as to escape the air that is caught in between the magnetic tape at the time of winding up thereof as soon as possible, and each of the concave portions 18 is formed gradually wider as approaching to the outer periphery. However, even in the tape reel 10 having such concave portions 18 on the lower flange 13, generation of winding irregularities has not been prevented substantially due to inadequate or improper escape of the air. Furthermore, by escaping the air being caught together with the running magnetic tape, the pressure given from outer periphery of the wound magnetic tape to inner side of the wound magnetic tape is increased. Accordingly as shown in FIG. 18, at the inner side where a winding condition of the magnetic tape T is loose, the surface of the wound magnetic tape forms moderate wavy bumps and dips, which causes problems of [crease] or [looseness].
The present invention has been made in view of the above-described problems, and when winding up a tape, one aspect of the present invention is to provide a tape cassette having tape reels capable of winding up the tape uniformly without causing winding irregularities and without incurring deformation.
The above-described problems may be solved by a structure of an aspect of the present invention, and means of solving the problems are described in detail hereunder.
A tape cassette according to one aspect of the present invention includes at least one tape reel having a flange at a hub unit on which a tape is wound. Further in the tape cassette of the invention, a flange of the tape reel has at least one concave portion to escape the air formed within the inner surface of the flange, and at least one of such tape reels is included within a tape cassette shell. The concave portion provided on the inner surface of the flange becomes larger at a circumferential cross-sectional area as approaching to the inner side nearer to the hub unit.
In such tape cassette, each of the concave portions of the flanges of the tape reel has the larger circumferential cross-sectional area as approaching to the inner side nearer to the hub unit, so that an amount of escaped air becomes more as approaching to the inner side. Accordingly, in a state that the tape is wound up, an amount of the air caught in between the tape may become less as approaching to the inner side, and more as approaching to the outer periphery, so that a pressure of the wound magnetic tape at the outer periphery may be reduced and may not reach the inner side, and the magnetic tape at the inner side may not be deformed when wound up. At the same time, an amount of air being caught by the concave portions may be restrained so that slide to the width direction between the overlapped magnetic tape may be inhibited with a result that winding irregularities may be effectively prevented and a good shape may be maintained.
In the tape cassette according to the present invention, the concave portions of the flange of the tape reel may have basically constant depth to the lateral direction, and may have broader width as approaching to the inner side nearer to the hub unit. In such tape cassette, mechanical strength of the tape reel may not be decreased by the concave portions, and an amount of the escaped air may be increased as approaching to the inner side and the wound form of the tape becomes a proper wound form.
In the tape cassette according to the present invention, the concave portions may be such that a cross-sectional form to the radial direction may have substantially constant depth. In such the tape cassette, an amount of escaped air may be set up by the width of the concave portions.
In the tape cassette according to the present invention, the concave portions may be such that a cross-sectional form to the radial direction may be deeper as approaching to the inner side. In such the tape cassette, an amount of escaped air may further be increased gradually as approaching to the inner side to provide even more proper wound form.
In the tape cassette according to the present invention, corner sections from the wall surface to the bottom surface of the concave portions of the tape reel may be made rounded to form curved surfaces. In such tape cassette, smooth flow of the air may be created at the concave portions when the tape reel rotates to effectively restrain the amount of air being caught with the wound tape.
In the tape cassette according to the present invention, the concave portions may be provided by plural number, and may be disposed at even angle intervals with the hub unit as the center. In such the tape cassette, the tape reel may have a good rotation balance, so that there may occur no tape reel deflection at the time of high-speed rotation.
In the tape cassette according to the present invention, a plurality of the concave portions of the flange of the tape reel may be disposed in proximity to each other around the outer periphery of the hub. In such the tape cassette, the air being caught may be escaped in comparatively equal quantity around the entire rim of the tape reel when the magnetic tape is wound up.
As described above, in a tape cassette of the present invention, there is provided at least one concave portion on an inner surface of a flange of a tape reel included in a cassette shell, wherein a cross-sectional area, that is, a cross-sectional area made by an arc-shaped cross section is made larger as approaching to the inner side nearer to a hub unit. In the case of one-flange type tape reel, the concave portions are provided on an inner surface of the flange where a tape is wound. In the case of the two-flange type tape reel, such concave portions may be provided on both opposing inner sides of the two flanges or on an inner side of one of flanges of the tape reel.
The concave portions may be one provided on the inner surface of the flange or plural numbers. In the case of providing a plurality of concave portions, it is desirable that they are disposed at even angles with a hub unit as their center. The concave portions may be made formed between the position tangent to the hub unit and the outer rim on the inner surface of the flange. Considering that winding irregularities or deformation of the tape are easy to occur on the inner side of winding, it is desirable that the concave portions are made formed on the way to the outer periphery from the position tangent to the hub unit. It is needless to say that they may be made formed in the shape covering from the position tangent to the hub unit to the outer periphery. In that case, the concave portions may have a shape which has the same width from the position tangent to the hub unit to the outer periphery.
It is important that the concave portions should have a large cross-section area as approaching to the inner side nearer to the hub unit. Namely, for the wound-up tape, winding irregularities or deformation are easy to occur on the inner side, so that, to prevent such occurrence, it is important that an amount of the air being caught should be made little on the inner side, and for that purpose, an amount of escaped air should be made more as approaching to the inner side. In order that the cross-section area of the concave portions should be made larger as approaching to the inner side, the shape of the concave portions may be made wider as approaching to the inner side, or the cross-sectional shape thereof may be made deeper as approaching to the inner side, or both shapes thereof may be adopted. For the concave portions whose depth is substantially constant but width is made wider as approaching to the inner side, an amount of air to be escaped may visually be recognized by the size of width and an appropriate shape of the concave portions may easily be obtained. Also by making the depth deeper as approaching to the inner side, the air may be effectively escaped at the inner side. However, if the depth of the concave portions is made too deep, there is a fear that mechanical strength of the flange may be impaired, so that it is desirable for the inner side to be made wider, and by doing so, it may become easy for the air to be escaped evenly to the circumferential direction. Furthermore, it is desirable that the concave portions should have a curved surface from the inner wall surface to the bottom surface. In comparison with the case that the inner wall surface and the bottom surface form square, air may flow smoothly and be effectively escaped.
When a plurality of the concave portions are provided on the tape reel, it is not necessary for the plurality of the concave portions to have the same stereoscopic shape, but for being capable of obtaining good rotation balance, it is desirable for them to be disposed symmetrically with respect to the hub as the center. When the plurality of the concave portions are provided, mutual proximity of the plurality of the concave portions at the outer rim position of the hub unit is preferable because air comes to be escaped in comparatively equal amount all around the tape reel, but such disposition of the concave portions is not an essential condition.